This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A207264 #7 Jul 22 2025 20:13:14 %S A207264 6,36,82,193,488,1087,2305,4932,10416,21716,45333,94798,198291,415803, %T A207264 874740,1845166,3902324,8273999,17581622,37429453,79812519,170419522, %U A207264 364296166,779456642,1669010171,3575965948,7665561753,16438759769 %N A207264 Number of nX3 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 1 1 and 1 0 1 vertically. %C A207264 Column 3 of A207269 %H A207264 R. H. Hardin, <a href="/A207264/b207264.txt">Table of n, a(n) for n = 1..210</a> %F A207264 Empirical: a(n) = 5*a(n-1) -9*a(n-2) +12*a(n-3) -22*a(n-4) +25*a(n-5) -16*a(n-6) +21*a(n-7) -17*a(n-8) +a(n-9) -6*a(n-10) +6*a(n-11) +a(n-12) +2*a(n-13) -2*a(n-14) for n>15 %e A207264 Some solutions for n=4 %e A207264 ..0..0..1....1..1..1....0..1..0....0..1..0....0..1..0....1..1..1....1..0..1 %e A207264 ..0..0..1....1..1..1....0..0..1....1..0..0....1..1..0....1..0..1....0..0..1 %e A207264 ..1..1..1....1..0..1....1..0..0....0..0..1....0..1..0....1..0..1....0..0..1 %e A207264 ..0..0..1....0..0..1....0..1..0....0..1..0....0..0..1....0..1..0....1..0..0 %K A207264 nonn %O A207264 1,1 %A A207264 _R. H. Hardin_ Feb 16 2012